Fuel systems in gas turbine engines, in order to bum fuel efficiently and to provide rapid burning, employ swirlers to evenly distribute a uniform fuel-air mixture within the combustion chamber. The swirlers, thus, facilitate the fuel-air mixture to complete the combustion reaction prior to exiting the chamber. Pressurized air from a conventional compressor positioned upstream of the combustor and fuel supplied from a fuel nozzle, are mixed upstream of the swirler. The fuel-air mixture in the combustion chamber is ignited to generate combustion gases.
Typically, swirlers include a centerbody having vanes extending radially outwardly therefrom. The vanes extend toward and are attached to an outer wall. The swirler extends into the interior of the combustion chamber and into the combustion zone through openings into the chamber.
During operation of the combustor, the swirler is bathed in hot combustion products from the ignition of the fuel in the combustion chamber. However, the inside of the swirler is cool as compared with the outside as the unignited fuel-air mixture channeled through the swirler vanes, is relatively cooler than the combustion products in the combustion zone surrounding the outer wall of the swirler. As a result, the outer wall of the swirler expands at a greater rate than the vanes or centerbody. A thermal gradient results between the hot outer wall and the cooler inner portion comprising the centerbody and vanes. The hot outer wall tries to expand as a function of its temperature, but is constrained by the cool centerbody and vanes which expand to a lesser extent.
Due to the differential thermal growth and movement between the outer wall and inner centerbody and vanes, the swirler experiences undesirable stress. There is a high probability that the stress will result in a crack in the outer wall. The crack will propagate as the fuel-air mixture enters the crack and is ignited by the surrounding combustion zone. The outer wall will then be burnt away compromising the durability of the swirler.